But on the other hand, I have my energy back, I am no longer experiencing demotivation, and I no longer feel depressed.

Cool! Glad to hear you're feeling better. Welcome, I'll try to give this my best shot as you wrote a very earnest post. I've been vegan for only 4 months but I feel pretty great, better than when I was eating animal products. I owe that to eating a whole foods plant based diet. Meaning I eat lots of fruits, grains, pasta, and veggies. Sounds like you do something similar. Ok so let's unpack your post.

I got to a point where I was losing too much weight and was under a healthy BMI for my height.

What is a healthy BMI for your height - and what was your weight? Losing too much weight, what do you mean specifically? Maybe you were undergoing a detox because your body finally could cleanse itself of toxic animal products. Would be helpful to know your actual weight and body fat percentage, not just BMI.

At this point, I stopped loosing weight but I got extremely sick. I ended up being in the hospital for 2 weeks for an infection that the doctors said was as intense as it was because of my “lowered immune system”.

There is no property in meat or animal products that will improve your immune system. In fact it would decrease it because your body would be busy breaking down incompatible foods (meat) by increasing the acidity in your body and consuming energy to break down those foods, which the human body is not well equipped for compared to plant based foods.

The hospitalization sounds really terrible, I'm glad you survived that. You don't say what kind of infection it is, but I doubt your plant based diet has anything to do with it.

You mention a low appetite, depression (low energy as well, perhaps low serotonin and other hormones) and other low energy symptoms like lowered immune system. It sounds like something else is going on that's not to do with your diet. Hard to say what it is though. What is your gender, and do you have any chronic conditions? Do you exercise regularly? These things will impact your health and would be good to know.

It got to the point where some friends were so worried about me that I had to enroll in therapy. But even with therapy, I couldn’t figure out why I was so sad all the time.

Again I really doubt that eating meat or not has anything to do with this. People are sad sometimes. It's ok to be sad and suffer, it's part of the human experience. Of course you can rise above identifying with your suffering but that's maybe a different discussion.

I ended up going back to the doctor because I legitimately thought I might still have an infection because I couldn’t rationally explain to myself why I felt this way out of nowhere.

Sounds like hypochondria to me. You're diagnosing yourself with illnesses and submitting yourself to doctors and therapists over and over. Their job is to find and treat illnesses so if you go to doctors constantly I'm sure they'll find or make up something. I really don't know though I have hardly ever gone to doctors, but that's my impression of them.

He said my body had trouble absorbing iron and some other vitamins so he recommended that I either reintroduce some animal products in my diet (such as cheese and milk) or eat seafood a couple times a week.

That's ridiculous you can get vitamins from plant based food, there is no reason why animal products would be a better source of vitamins. Eat a well rounded plant based diet and if you're really into vitamins take a multivitamin. Why eat meat when you can just take a pill that has iron in it, not to mention just eating spinach.

I don’t know what to do. I feel so lost. Friend, family, doctors, and dietitians are telling me that this is necessary but I feel so guilty. But on the other hand, I have my energy back, I am no longer experiencing demotivation, and I no longer feel depressed.

It sounds to me like you want me to give you an excuse to eat meat. These folks giving you these recommendations and pressuring you are just brainwashed into the mainstream groupthink of eating meat. You don't have to do it. Although you DO need to muster up more strength in your willpower and determination than you are showing right now. I would say you need a good exercise routine, it should help with this low motivation and low energy.

I would just love to hear if anyone else has gone through something similar. Were you able to overcome it on a vegan diet? If so, how?

I don't know what your condition is to know whether I've overcome it or not. So I can't really say either way. What I will say however is that I'll be vegan for life no matter what. Yeah the island scenario? I'll starve and have a pig for a friend. I'm not into torturing animals for my pleasure. It just so turns out that being vegan is way healthier than eating meat. I know you have a good heart because you feel the same way. So don't be discouraged. People get sick, people get sad. I've been there, and have had depression and suicidal thoughts and all that stuff. Honestly I've never been more positive and happy than since I've gone vegan but I don't know if it's a coincidence or not. It's coincided with other things I've done, such as a continuous spiritual practice.

Well, good luck to you friend. I think if you get your energy back and re-commit yourself that you were on the right path from the beginning, you'll feel better. I'd honestly stop going to all those doctors and therapists so much as well, I don't think it's serving you at this point. Remember, the answers, the truth, is inside of you. Whenever you are in doubt look within. You'll have the answers there.